The visual function assessment module allows non-invasive assessment of eye structure and function, which is critical for clinically-relevant studies of the visual system employing animal models. It affords investigators the tools necessary to systematically interrogate normal visual function and the consequences on vision when normal processes go awry. The expertise and instrumentation available in this module exceed resources of individual investigators? laboratories and provide access to equipment that, if purchased by a single investigator, would rapidly deplete precious resources. The module provides skilled expertise, training and essential, state- of-the-art equipment to perform the following assessments: (1) electroretinography (ERG), (2) optokinetic tracking response (OKR), (3) spectral domain optical coherence tomography (OCT), (4) fundoscopy, (5) fluorescein angiography (FA), (6) slit-lamp biomicroscopy, (7) intraocular pressure (IOP). For ERGs, the module offers the expertise of a highly skilled PhD electrophysiologist who can perform sophisticated retinal function evaluation and it also offers training for investigators in execution of routine ERGs. A PhD level scientist directs the module and provides training for laboratory personnel for other assessments (OCT, FA, OKR etc). Instruments available in this module include the Celeris Fully Integrated High Throughput ERG Testing system, the Phoenix MICRON Ganzfield ERG, the Bioptigen Spectral Domain Ophthalmic Imaging System (Envisu R2200), the image-guided MICRON IV OCT, two Phoenix MICRON IV in vivo high-resolution retinal imaging microscopes for FA and fundoscopy, the Topcon SL-DR slit-lamp and two hand-held tonometers for rapid IOP assessment. These instruments have been widely used by a number of Culver VDI investigators resulting in collaborations and shared publications/presentations that fully justify formalizing these services as a module. Access to this equipment will enhance vision research for established NEI investigators, first-time NEI R01 investigators, and scientists new to the field of vision research. The activities of the core will be achieved through the following aims: Aim 1. Provide core investigators access to state-of-the-art instrumentation for in vivo visual function analysis and in vivo imaging of the visual system. Aim 2. Provide expert technical assistance and training in the use of the shared instrumentation within the module. Aim 3. Maintain module instrumentation in good working condition, manage usage in a manner that will facilitate productivity, collaboration and the development of novel projects that address major sight-threatening diseases.